This invention relates to an improved process for the preparation of alkylamine from olefin by first hydrohalogenating the olefin to form haloalkane then reacting the haloalkane with amine to form alkylamine. The alkylamine, thus formed, is then heat-treated with an aqueous alkaline or alkaline earth metal hydroxide at a temperature and for a period of time sufficient to minimize the formation of flocculent precipitate during product storage.
As a class, many alkylamines and products derived therefrom, especially linear tertiary amines, are useful as surface active agents, e.g., surfactants, soaps, cleansing agents, and other personal care products. Processes for the formation of alkylamines are known. U.S. Pat. No. 4,024,189 discloses one such process and is incorporated herein by reference as if fully set forth, wherein alkylamines, most notably alkyldimethylamines, are produced starting with a mixed olefin feed, which may contain vinyl olefins and internal olefins, or vinyl olefins and vinylidene olefins, or a mixture of vinyl olefins, internal olefins and vinylidene olefins.
Initially, where vinylidene olefins are present in appreciable amounts, the olefin feed can be selectively isomerized to convert the vinylidene olefins to branched chain internal olefins. The mixture of vinyl olefins and internal olefins is then hydrohalogenated in the presence of a free radical catalyst to produce haloalkanes. The haloalkanes are then selectively dehydrohalogenated whereby 1-haloalkanes are substantially unaffected while secondary haloalkanes are converted to olefins and separated from the 1-haloalkanes. Amination of the 1-haloalkanes is conducted with an amine having at least one replaceable hydrogen atom, thus converting the 1-haloalkanes to amine hydrohalides. Following this operation, the amine hydrohalides in the intermediate product are converted into amines, preferably by a neutralization reaction with a suitable base thus forming a halide salt of the base used in neutralization. The amines thus produced are recovered from the halide salt.
U.S. Pat. No. 4,982,024 discloses a process for the selective dehydrohalogenation of a feed comprised of a mixture of primary, secondary and tertiary alkylbromides; conversion of the secondary and tertiary alkylbromides to olefins, with minimal conversion, if any, of the primary alkylbromides; and simultaneous separation of primary alkylbromides from the reaction mixture. This process allows for the use of more mixed olefin feeds rather than the high purity alpha olefin feeds required for use in the process disclosed in U.S. Pat. No. 4,024,189.
In both of the aforementioned processes, a considerable amount of flocculent precipitate (hereinafter referred to as "floc") tends to form during long term storage of the alkylamine (ADMA) product. Floc occurs in ADMA samples in either of two main descriptive forms. The first form is a "blue haze" which appears in product column feed and or distillate samples. The second form of floc appears as a solid precipitate in the bottom of samples bottles, which may occur in the samples after a few days of storage. The floc has been identified as a quaternary ammonium salt, which is believed to be n-alkyltrimethylammonium halide and/or dialkyldimethylammonium halide or mixtures thereof which is relatively insoluble in the alkylamine products. It is theorized, although the process of this invention is not bound by such theory, that much of the floc is formed by the reaction of the alkylamine product with an alkyl bromide that inadvertently co-distills with the alkylamine product. The formation of quaternary ammonium salts, commonly proceeds by the Menschutkin reaction, as exemplified in Equation I for quaternary ammonium bromides. EQU R.sub.3 N+RBr&lt;.dbd.&gt;R.sub.4 N+Br.sup.- (I)
During long term storage and/or overseas transportation of the alkylamine product, the product may react with the alkyl bromide to form the insoluble quaternary ammonium salts. Precipitation of the salts thus formed tends to give the product a cloudy appearance. Therefore, there exists a clear and present need for processes which reduce the amount of floc which forms during the storage of alkylamines.
It is, accordingly, a primary objective of this invention to fulfill this need, and others. In particular, it is an objective to provide for an improvement to well known prior art methods for producing alkylamines so as to substantially reduce the tendency to form floc when the product is transported or stored.